Melt spinning

ABSTRACT

In combination with melt spinning means comprising a melt spinning head arranged for extruding vertically downwardly a plurality of molten streams of a thermoplastic and a bath arranged to receive the streams from the head and to contain a liquid to quench and thereby solidify the streams to form filaments, the improvement comprising annular baffle means suspended in the bath in a position to surround the plurality of molten streams or filaments as they move substantially vertically downwardly, the baffle means comprising a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge of each respective member extending to a distance from the surface of the liquid greater than the corresponding distance for any other of the members of smaller diameter and lesser than the corresponding distance for any other of the members of greater diameter.

United States Patent Arnett, Jr. et a1.

[54] MELT SPINNING [72] Inventors: Joseph W. Arnett, Jr., Sevema Park;David W. Nor-wood, Baltimore, both of Md.

[73] Assignee: Concorde Fibers, lnc., Columbia,

[22] Filed: June 8, 1970 [21] Appl. No.: 44,371

[52] US. Cl; ..264/178 F, 18/8 F, 264/40 [51] Int. Cl. ..D0ld 5/08 [58]Field of Search ....264/l8l, 40, 178 F, 178, 180;

18/8 B, 8 F, 8 WA, 12'IT [56] References Cited 2/ l 962 France ..264/178 F 5/1966 Japan ..264/178 F Primary Examiner-Jay H. Woo Attomey-Nolteand Nolte [5 7] ABSTRACT In combination with melt spinning meanscomprising a melt spinning head arranged for extruding verticallydownwardly a plurality of molten streams of a thermoplastic and a batharranged to receive the streams from the head and to contain a liquid toquench and thereby solidify the streams to form filaments, theimprovement comprising annular baflle means suspended in the bath in aposition to surround the plurality of molten streams or filaments asthey move substantially vertically downwardly, the baffle meanscomprising a plurality of radially spaced concentric annular foraminousmembers each having its upper edge no lower than the surface of theliquid and the lower edge of each respective member extending to adistance from the surface of the liquid greater than the correspondingdistance for any other of the members of smaller diameter and lesserthan the corresponding distance for any other of the members of greaterdiameter.

8 Claims, 3 Drawing Figures MELT SPINNING This invention relates to animprovement in melt spinning in which a plurality of at least partiallymolten streams of thermoplastic is extruded into a liquid quench bath inwhich there is provided a baffle surrounding the streams which baffle isof novel construction for this purpose.

In a conventional form of melt spinning a thermoplastic to formfilaments, a spinning head is mounted above a bath containing aquenching liquid and a plurality of closely adjacent molten streams ofthe thermoplastic are extruded substantially vertically downwardly fromthe spinning head into the quenching liquid through which they are leadsubstantially vertically downwardly without being diverted from thispath by guide means until they have solidified into filaments havingsubstantially non-tacky surfaces. The passage of the streams andresultant filaments into and through the liquid results in circulationand turbulence of the liquid in 'the vicinity of the streams orfilaments. Specifically, friction between the thermoplastic streams orfilaments and the quench liquid causes the streams or filaments to dragliquid downwardly with them which liquid circulates upwardly again,creating in additionto such circulation in the vicinity of the streamsor filaments also turbulence in the vicinity of the streams orfilaments. Of course, it is not intended'to limit the description of thepresentinvention to any particular theory asto the circulation andturbulence of the quench liquid in the vicinity of the thermoplasticstreams or filaments but, in general, it may be said that there is somesort of circulation and turbulence. This circulation and turbulence canbe troublesome as it may cause the thermoplastic streams or filamentswhile still highly tacky to contact each other and, thus, damage oneanother or permanently fuse together. To

alleviate this problem, there has been proposed the use I of variousannular baffles around the thermoplastic streams or filaments. Thepresent invention provides a baffle of novel construction for thispurpose which baffle is particularly effective and is also simple andeconomical to fabricate.

The baffle of the present inventions is in the form of a plurality ofradially spaced concentric annular foraminous members each having itsupper edge no lower than the surface of the liquid and the lower edgeportion of each respective member extending a distance from the surfaceof the liquid greater than the corresponding distance for any other ofthe members of smaller diameter and lesser than the correspondingdistance for any other of the members of greater diameter. The baffle issuspended in the quenching liquid with the group of closely mutuallyadjacent molten streams issuing from a spinneret in the spinning headpassing concentrically through the innermost member of the baffle. It ispreferred that the baffle be constituted of at least three of themembers. Tl-Ie foraminous members diminish circulation and resultantturbulence of the quench liquid in the vicinity of the molten streams ortacky filaments sufficiently to essentially completely eliminate contactthereof with one another while still permitting the liquid to circulateand mix sufficiently in the vicinity of the molten streams or tackyfilaments to hasten the formation of non-tacky filaments. In thisrespect, it should be appreciated that liquid movement in the vicinityof the molten streams or tacky filaments is desirable rather thanundesirable to the extent that by preventing the formation of arelativelystagnant heated body of quench liquid in the vicinity of themolten streams or tacky filaments undue delay in the attaining of anon-tacky state is avoided.

Another factor is that motion and turbulence of the liquid tends to begreatest at the surface. In this respect, it is noted for one thing thatthe liquid flows most readily at the surface toward the molten streamsor filaments as part of a chain effect of liquid motion which has itsstarting point in the frictional drag between the downwardly movingmolten streams or filaments and the surrounding liquid. The reason forthis phenomenon is that a hypothetical top layer of liquid is hamperedin its motion by adjacent liquid only at its bottom face whereas otherhypothetical layers of the liquid are hampered at both their top andbottom faces by adjacent liquid. Somewhat below the surface of theliquid, the liquid adjacent the filaments attains a more or less steadystate streamlined flow which does not tend to cause the filaments tocontact each other. It is found that the degree of hampering of themovement of the liquid around the molten streams or filaments may bestepped down from a maximum at the surface of the liquid and thencompletely eliminated when the liquid flow is adequately streamlined.

These various considerations are taken into account in the presentinvention. Hence, flow of the liquid is hampered by progressively fewerlayers of foraminous baffle structure as the distance from the surfaceincreases. The present invention tends to optimize the desired balancewhich involves on the one hand obtaining'sufiicient liquid motion in thevicinity of the molten streams or filaments to hasten the coolingthereof while on the other hand avoiding liquid motion of such magnitudeor turbulence as would tend to bring the molten streams or tackyfilaments into mutual contact. Hence, restriction of the motion of theliquid is applied to the greatest extent where such restriction is mostimportant to the avoiding of excessive liquid motion and turbulence andrestriction is progressively stepped down as it becomes less necessary.

The invention will now be described by reference to a specific.embodiment thereof as illustrated in the drawings, in which:

FIG. 1 is a partially schematic elevation view of a spinning head-quenchbath assembly in operation and incorporating baffle means according tothe invention;

FIG. 2 is an isometric view of the baffle means of FIG. 1; and

FIG. 3 is a detail, partly in section of the baffle means of FIG. 2. v

To a spinning block or head 1 through a conduit 2 is fed moltenthermoplastic (FIG. 1). The molten thermoplastic is extruded or spunvertically downwardly through the multiple closely adjacent orifices oftwo spinnerets (not shown) in the spinning block 1. There are thusformed two sets 3 and 3' of closely adjacent molten streams ofthermoplastic which subsequently are solidified to form filaments. Afterpassing a short distance through the air, the sets 3 and 3 enter aquench liquid 4, generally water, contained in a bath or tank 5.Suspended in the bath 5 is a baffle assembly 6 including two sets 6a and6b of annular baffles. The bafile assembly 6 is so arranged that intheir vertically downward movement the sets 3 and 3 of molten streams orfilaments pass concentrically through respective sets of baffles 6a and6b. It will be appreciated that simple brackets or the like (notillustrated) are provided to support the baffle assembly 6 in the bath5.

A bracket 7 interconnects the two sets 60 and 6b of baffles. Each set ofbafi'les is composed of three concentrically arranged foraminous rings8, 9, and 10 of progressively greater diameter and greater axial length(FIG. 2). Conveniently, bracket means (not shown) are provided on a wallof the bath adjacent bracket means 7 to cooperate with bracket means 7to support the baffle assembly 6.

To facilitate such operation as threading of the apparatus duringstart-up, each set 6a and 6b of baffles is constructed in the form oftwo semi-circular units which are manually disengageable from oneanother along a diameter perpendicular to the long axis of the assembly6, as illustrated in FIG. 2 with respect to the set 6b of baffles. Theouter semi-circular sub-assembly is provided with solid end plates 11aand 11b and the inner semi-circular sub-assembly is provided with solidend plates 11c and 11d. Provided on respective end plates 11a and 11bare respective hooks 13 and 13. Provided in respective end plates 11cand 11d are respective slots 12 and 12' positioned to receive hooks 13and 13', respectively, for releasable fastening together of the twosemi-circular sub-assemblies. The hook is simply received in thecorresponding slot with the downwardly directed portion of the hookengaging behind the slotted end plate (FIG. 3).

Spanner members 140 and 14b lend additional rigidity to the outersemi-circular baffle sub-assemblies. Spanner 15 functions similarly withrespect to the subassembly composed of the inner semi-circular bafflesub-assemblies and bracket 7 and also functions to rigidly fasten to oneanother the respective inner semicircular sub-assemblies.

The following is noted as a typical but non-limiting example of therelative dimensions involved. Each set 3 and 3' of filaments is 6%inches in diameter. Baffles 8, 9, and are respectively 8 inches, 10inches, and 12 inches in diameter and respectively 2% inches, 5 inchesand 6% inches in axial length and are positioned with their top edgesabout 1/4 inch above the liquid surface in the bath. The baffles 8, 9and 10 are each constituted of expanded metal having /;-inch openingsseparated by one-fourth inch.

While the invention has been described be reference to a specificembodiment thereof, it is to be understood that such description is notintended as a limitation upon the scope of the invention as defined bythe appended claims.

What is claimed is:

I. In a method of producing filaments of a thermoplastic in which thethermoplastic is extruded substantially vertically downwardly in theform of a plurality of closely mutually adjacent molten streams into aliquid quench bath from a location vertically spaced above the surfaceof the bath and passed substantially vertically downwardly through theliquid at least until I trudin the filaments into a zone in the bath inwhich circula ion and turbulence of the liquid in the bath due topassage therethrough of the filaments is diminished whereby any tendencyof the molten streams or the resultant filaments while stillsubstantially tacky to be brought into mutual contact by circulation orturbulence of the liquid is diminished, the zone extending downwardlyfrom the surface of the bath, surrounding the plurality of moltenstreams of filaments and being defined by a plurality of radially spacedconcentric annular foraminous members each having its upper edge nolower than the surface of the liquid and the lower edge portion of eachrespective member extending a distance from the surface of the liquidgreater than the corresponding distance for any other of said members ofsmaller diameter and lesser than the corresponding distance for anyother of said members of greater diameter.

2. A method according to claim 1, wherein said thermoplastic is asynthetic resin of the type which can be solidified by cooling and whichtends when extruded as hot liquid, to form tacky filaments.

3. A method according to claim 1, wherein said bath is of aqueous type.

4. In combination with melt spinning means comprising a melt spinninghead arranged for extruding vertically downwardly a plurality of moltenstreams of a thermoplastic and a bath arranged to receive the streamsfrom the head and to contain a liquid to quench and thereby solidify thestreams to form filaments, the head being vertically spaced above thesurface of the liquid, the improvement comprising annular baffle meanssuspended in the bath in a position to surround the plurality of moltenstreams or filaments as they move substantially vertically downwardly,said baffle means comprising a plurality of radially spaced concentricannular foraminous members each having its upper edge no lower then thesurface of the liquid and the lower edge portion of each respectivemember extending a distance from the surface of the liquid greater thanthe corresponding distance for any other of said members of smallerdiameter and lesser than the corresponding distance for any other ofsaid members of greater diameter.

5. Apparatus according to claim 4, wherein the innermost one of saidmembers is outwardly spaced from said plurality of streams by a fractionof the diameter of said plurality of streams.

6. Apparatus according to claim 5, wherein outer ones of said membersare outwardly spaced from said innermost one by distances approximatelysimilar to said fraction of said diameter.

7. Apparatus according to claim 5, wherein said innermost member extendsa distance below said surface approximately one-half said diameter.

8. Apparatus according to claim 7, wherein the outermost one of saidmembers extends a distance below said surface approximately equal tosaid diameter.

1. In a method of producing filaments of a thermoplastic in which thethermoplastic is extruded substantially vertically downwardly in theform of a plurality of closely mutually adjacent molten streams into aliquid quench bath from a location vertically spaced above the surfaceof the bath and passed substantially vertically downwardly through theliquid at least until the molten streams have solidified to formsubstantially non-tacky filaments, the improvement comprising extrudingthe filaments into a zone in the bath in which circulation andturbulence of the liquid in the bath due to passage thErethrough of thefilaments is diminished whereby any tendency of the molten streams orthe resultant filaments while still substantially tacky to be broughtinto mutual contact by circulation or turbulence of the liquid isdiminished, the zone extending downwardly from the surface of the bath,surrounding the plurality of molten streams of filaments and beingdefined by a plurality of radially spaced concentric annular foraminousmembers each having its upper edge no lower than the surface of theliquid and the lower edge portion of each respective member extending adistance from the surface of the liquid greater than the correspondingdistance for any other of said members of smaller diameter and lesserthan the corresponding distance for any other of said members of greaterdiameter.
 2. A method according to claim 1, wherein said thermoplasticis a synthetic resin of the type which can be solidified by cooling andwhich tends when extruded as hot liquid, to form tacky filaments.
 3. Amethod according to claim 1, wherein said bath is of aqueous type.
 4. Incombination with melt spinning means comprising a melt spinning headarranged for extruding vertically downwardly a plurality of moltenstreams of a thermoplastic and a bath arranged to receive the streamsfrom the head and to contain a liquid to quench and thereby solidify thestreams to form filaments, the head being vertically spaced above thesurface of the liquid, the improvement comprising annular baffle meanssuspended in the bath in a position to surround the plurality of moltenstreams or filaments as they move substantially vertically downwardly,said baffle means comprising a plurality of radially spaced concentricannular foraminous members each having its upper edge no lower then thesurface of the liquid and the lower edge portion of each respectivemember extending a distance from the surface of the liquid greater thanthe corresponding distance for any other of said members of smallerdiameter and lesser than the corresponding distance for any other ofsaid members of greater diameter.
 5. Apparatus according to claim 4,wherein the innermost one of said members is outwardly spaced from saidplurality of streams by a fraction of the diameter of said plurality ofstreams.
 6. Apparatus according to claim 5, wherein outer ones of saidmembers are outwardly spaced from said innermost one by distancesapproximately similar to said fraction of said diameter.
 7. Apparatusaccording to claim 5, wherein said innermost member extends a distancebelow said surface approximately one-half said diameter.
 8. Apparatusaccording to claim 7, wherein the outermost one of said members extendsa distance below said surface approximately equal to said diameter.